That's why I've said countless of times already that late join games should not affect your WLR.
Too bad that ND refuses to listen to sensible feedback, unless they can make more money with it... hmmm, maybe they should release a DLC for that (no wins/losses for late join games for $0.99).
No win/loss from late join games
1 month - 0.99
1 year - 9.99
Lifetime - not available